Dear Doctor K: My son jerks his neck constantly. Why does he have this tic? Is it dangerous? What can we do about it?

Dear Reader: Tics are upsetting ó both to the person who has them and to the people who see them. We like to feel in control of our world. A sudden, uncontrollable, rapid repetitive movement (called a motor tic) says weíre not in control. Since your neck moves only when you want it to, itís disturbing to see your son doing something you know you could control. You can, but he canít.

Neck jerking is a common tic. Other kinds of tics include sudden, uncontrollable sounds or vocalizations (vocal tics), eye blinking, sniffing and throat clearing.

Tics are thought to be inherited neurological disorders that affect the bodyís motor system. They also can be caused by head injury or certain drugs, such as stimulants. Many kids with tics lose them by the time they are young adults. Hopefully, that will be true of your son.

People with tic disorders describe an urge building up inside them before the tic appears, followed by a feeling of relief after the tic has passed. After making an effort to suppress a tic, the person usually has a burst of tics to relieve a buildup of the inner sensation.

When both motor and vocal tics are present and last for more than one year, the disorder is named Touretteís syndrome. Fatigue, anxiety and stress often make symptoms worse.

If a stimulant medication is causing your sonís tic, it might be worth stopping it, or substituting another stimulant drug in its place. Mild tics do not require treatment unless they are socially embarrassing or interfere with your childís life.

I do not believe that tics have psychological causes, but I do believe they can have psychological effects. I remember vividly a plane trip I once took to Seattle. Every few minutes, the woman sitting next to me would jerk her head and cry out "Eeeahhhh." I realized she probably had Touretteís syndrome and couldnít control it, but I was annoyed: It was going to be hard to concentrate on my reading.

She must have seen my expression because she said: "Iím so sorry, sir, but I have a medical condition that causes this. I wish I could control it, but I canít. And Iíve got to get to my sister in Seattle." I will never forget the expression of shame on her face.

If your son is disturbed by his tics, psychological counseling and behavior training can be effective. For example, a child may be taught to recognize that a tic is beginning and perform another movement that is incompatible with the tic.

Page 2 of 2 - Some people have severe tics that cause them to hurt themselves, by hitting or biting, for instance.

Severe tics can be treated with medications that affect certain chemical messengers in the nervous system. A number of other medications, including injections of botulinum toxin (Botox and others), also may be effective.